Electrophotographic plate and the method for producing the same

ABSTRACT

A PHOTOSENSITIVE PLATE HAVING A PHOTOCONDUCTIVE LAYER COMPOSED OF A DISPERSED SYSTEM OF PHOTOCONDUCTIVE MATERIAL AND RESIN SANWICHED BETWEEN A CONDUCTIVE LAYER AND A TRANSLUCENT INSULATIVE LAYER IN THE ABSENCE OF A SOLVENT. THE PHOTOCONDUCTIVE LAYER IS A SOLID LAYER PRODUCED BY   POLYMERIZATION OF A LIQUID RESIN MIXTURE PRODUCED BY DISPERSING A PHOTOCONDUCTIVE SUBSTANCE INTO A LIQUID POLYMERIZABLE RESIN NOT CONTAINING A SOLVENT.

Aug. 29, 1972 TAKAO KOMlYA ETAL 3,537,659

' ELECTROPHOTOGRAPHIC PLATE AND THE METHOD FOR PRQDUCING THE SAME FiledSept. 12, 1967 United States Patent ()1 hce 3,687,659 Patented Aug. 29,1972 U.S. C]. 96-15 11 Claims ABSTRACT OF THE DISCLOSURE Aphotosensitive plate having a photoconductive layer composed of adispersed system of photoconductive mate rial and resin sandwichedbetween a conductive layer and a translucent insulative layer in theabsence of a solvent. The photoconductive layer is a solid layerproduced by polymerization of a liquid resin mixture produced bydispersing a photoconductive substance into a liquid polymerizable resinnot containing a solvent.

This invention relates to improved electrophotographic plates and moreparticularly to the improved three-layer photosensitive platescomprising a photoconductive layer interposed between a conductive layerand a translucent insulative layer and to methods for producing suchphotosensitive plates useful in electrophotographic processes such asthe so-called Carlson process, P.I.P. process, other conventionalprocesses or processes developed by the inventors of this invention anddescribed hereinafter.

Conventional electrophotographic processes wherein photosensitive platesof this kind are used, are described in U.S. Pats. Nos. 3,124,456 issuedto T. H. Moore and 3,041,164 issued to R. M. Blakney.

In Pat. No. 3,041,164, the photosensitive plate is prepared by providinga photoconductive layer on a conductive base and by providing thephotoconductive layer with a protective overcoating layer, and a staticlatent image is formed on said overcoating layer by the Carlson process.In Pat. No. 3,124,456, the photosensitive plate is prepared by providinga photoconductive layer comprising CdS or CdSe and binder resin on aconductive base, and by providing a translucent insulative layerthereon. Charging is carried out simultaneously as the original image isirradiated upon the translucent insulative layer side of saidphotosensitive plate, and a static latent image is formed on thetranslucent insulative layer by different build-up of chargeattributable to different time constants caused by different impedancesin the photoconductive layer portions disposed in the light-and-darkportion of the original image.

Three-layer photosensitive plates of this invention are preferablyapplied to the processes described in copending applications Ser. Nos.563,899 and 571,538. Such processes can be summarized as follows. Aphotosensitive plate having a photoconductive layer interposed between aconductive layer and a translucent insulative layer is used, and thesurface of the translucent insulative layer is initially charged, and bythe field of such charge, a layer of charge is bound between thephotoconductive layer and the translucent insulative layer or in theneighborhood thereof. Then, by the external field of the bound charge,and corona discharge of opposite polarity to the polarity of saidinitial charge (or AC corona discharge) and simultaneous irradiation ofan original image, a static latent image is formed on the surface of thetranslucent insulative layer. Then light rays are irradiated on thewhole surface of the translucent insulative layer to increase thecontrast of the static latent image formed on the surface of thetranslucent insulative layer.

In each of the above cases, a static latent image is formed on thesurface of the translucent insulative layer and said static latent imageis developed with charged particles (toner). Thereafter the developedimage is transferred to copying material, and the transferred image isfixed to produce an electrophotographic image. Therefore, it is possibleto make copies on ordinary papers. The produced image has a naturalfeeling and is as readable as the image of the printed matters and sinceit is not necessary to use special photosensitive paper such copy iseconomical. With regard to the photosensitive plate, since thephotoconductive layer is coated with a translucent insulative substance,deterioration and fatigue of the surface of the photoconductive layerare prevented without causing appreciable damage or deterioration byphysical effects such as friction or pressure by selecting theinsulative layer to have high resistivity and resistance to wear. Also,resistance to humidity or various gases is high, and since it is notnecessary for the photoconductive layer itself to retain electriccharge, it is possible to use highly sensitive photoconductive substanceof low resistivity not usable in the conventional Carlson process, andyet remarkably increase sensitivity. Thus, a number of advantages attenduse of such three-layer plates. Since electrophotographic processes inwhich such photosensitive plates are used have many advantages, therehave been proposed many applications in addition to the above-mentionedprocesses, and it is considered that many applications will be furtherdeveloped in the future.

However, there is no satisfactory heretofore known method for producingthe resin for binding the fine powder photoconductive substancescomprising the photoconductive layer, or for producing suchphotosensitive plates, and at present it is impossible to supplyphotosensitive plates of suffieiently high quality.

Conventional photosensitive plates are produced by providing aphotoconductive layer comprising a dispersion of fine powderphotoconductive substances. such as zinc oxide, cadmium sulfide, cadmiumselenide or the like in a resin binder, on a conductive layer such asiron or aluminum, and by providing a translucent insulative layer havinghigh resistance to wear, such as polyester resin, polyethylene resin orthe like.

As binders for photoconductive substances, shellac, wax or such likenatural resin or silicone resin, vinyl resin, phenol resin, polyesterresin, vegetable oil, alkyd resin, styrol resin, melamine resin, acrylicacid ester resin, polycarbonate resin or like resins were used. Suchconventional photosensitive plates are produced in accordance with thefollowing method. Liquid in the form of paint is prepared by uniformlymixing the fine powder photoconductive substance, the resin binder, andthe solvent for said resin, and such liquid is coated on the conductivelayer. The translucent insulative layer is laid thereon to form thelayers into a single plate. Alternatively, a thermoplastic resin havinga low melting point is selected as the binder for the photoconductivesubstance, and the liquid paint, obtained as mentioned above, is coatedon the conductive layer. The coated conductive layer is sufficientlydried, and the translucent insulative layer is laid on thephotoconductive layer and is contacted by hot rollers to melt the binderresin and the translucent insulative layer is thus melt-adhered. -Inanother method the translucent insulative layer is adhered by anadhesive after the photosensitive layer is formed on the conductivelayer as mentioned above.

In the foregoing first method, the evaporation of a solvent isremarkably difl'icult, and thus the method is not practical. In thesecond method the translucent insula-' tive layer is irregularly spreadby heat, producing wrinkles,

and it is very diflicult to produce a smooth photosensi-. tive plate. Inaddition, an organic solvent is evaporated during the drying process,and therefore hygienic troubles and danger of fire are involved. In thethird method,

undesired wrinkles occur easily on the translucent insulative layer, thethickness of the translucent insulative layer becomes undesirablythicker by the thickness of the adhesive layer, and the sharpness of theproduced image is decreased. In all cases where photosensitiveplatesiare prepared by dissolving binder in a solvent, a little amountof the solvent or water or like volatile component's remain in thephotoconductive layer after the plate is dried, and thereforedeterioration of image properties occurs in several months when suchplates are exposed to ambient environment. I

-In each of the conventional methods, it is impossible to simply andsafely produce photosensitive plates of I sufficiently high quality.

An object of this invention is to provide photosensi- A further objectof this invention is to provide photosensitive plates which haveexcellent physical properties of hardness, resistance to bending, andsuflicient durability for repeated use and methods for producing thesame.

Another object of this invention is to provide photo sensitive plateshaving less change of latent image properties with passage of time andexhibiting constancy over extended periods.

A further object of this invention is to provide methods for producingphotosensitive plates in an economical and sanitary manner.

Another object of this invention is to provide methods for producingphotosensitive plates easily and safely.

This invention is characterized in that the photoconductive layer,comprising a photoconductive substance and a resin, of anelectrophotographic photosensitive plate comprising an underlyingconductive layer and an overlying translucent insulative layer is asolid layer prepared by polymerization of a liquid form resin, i.e., aliquid polymerizable resin precursor, of a mixture obtained bydispersing the photoconductive substance into the liquid formpolymerizable resin without a solvent. Such mixture is subjected topolymerization of said liquid resin in such state that the mixture isretained with a definite thickness between the conductive layer and thetranslucent insulative layer in producing the photosensitive plate.

The above objects and other objects and advantages of this inventionwill be easily and clearly understood from the following detailedexplanations of the invention and the drawings.

FIG. 1 shows the fundamental structure of the photosensitive plate ofthis invention.

FIG. 2 shows a first process for producing photosentive layer 1,photoconductive layer 2 provided between conductive layer 1 andtranslucent insulative layer 3. Layer 2 is a solid layer prepared bypolymerization of a liquid resin mixture in turn prepared by dispersinga photoconductive substance into "a liquid polymer v. resin precursornot containing a solvent.

Conductive layer 1 may comprise a plate of an electrostaticallyconductive substance such as iron, copper, aluminum or like metal,aluminum foil, tin foil or like metal foils, conductive paper or cloth,paper laminated with metal foil, or a metal layer vacuum-evaporated ontoplastic film. Translucent insulative layer 3 terial satisfying threerequirements, i.e., high resistance to wear, high electrical resistivityand high capability to retain static charge, and permeability toactivating radiation, as for example, the films of polyester resin,polyethylene resin,-polyamide resin, polypropylene resin,polyfiuoroethylene resin, or nitric acid ester or acetic acid ester ofcellulose or the like.

Photoconductive layer 2 may comprise inorganic photoconductivesubstances such as the mixture of one or more of the compounds selectedfrom .zinc' .oxide, titanium oxide, lead oxide, cadmium sulfide, cadmiumzinc sulfide, cadmium selenate, and the oxides of mercury, antimony,bismuth, thalium, indium, molybdenum, aluminum, tellurium or iodine, ororganic photoconductive substances such as anthracene or carbazole orimidazole. It is possible to enlarge the spectrum of thephotosensitivezone by absorbing sensitizing materials, such I asdye-stuffs in the above photoconductive materials. Among the above'photo conductive substances, the substances which are preferably usedin this invention are activated cadmium sulfide, cadmium selenate orsuch like highly photoconductive substances, and when these substancesare used,'it is possible to remarkably increase sensitivity. Zinc oxideis also T one of the preferable materials.

The binders forming the photoconductive layer 2 by binding saidphotoconductive substances dispersed therein may comprise polystyreneresin, acrylic resin, epoxy resin, polyester resin or such likepolymerizable liquid resins not containing a solvent.

prise liquid polymerizable synthetic resin monomer, liquid syntheticresins of lower polymerization but having polymerizability, and mixturesthereof with other resins dissolved thereinto. w

The following are examples: I e

(1) Liquid polymerizable monomers not containing a solvent: Styrenemonomer, methacrylic acid ester mono-- mer, epoxy monomer, such as themain component of Shell Epikote (trade name of Shell Chemical 00., Ltd)-828,-etc. v r

(2) Polymerizable resins of lower polymerization in the form of liquidnot containing a solvent: Epoxy resin, such as Shell Epikote 828,produced by condensation of 'epichlorohydrin with bisphenol A,containing a small amount of dimer or trimer, Shell Epikote 834,containing a larger amount of dimer or trimer, etc.

(3) Liquid monomer not containing a solvent into which another resin isdissolved: Vinyl type monomer with unsaturated polyester resin dissolvedtherein, epoxy monomer with vinyl acetate resin or phenol resindissolved therein, etc.

(4) Liquid form polymerizable resin of lower polym- I erization notcontaining a solvent, into which another resin is dissolved: Vinylacetate resin or phenol resin dissolved in liquid epoxy resin, etc.

According to this invention, the foregoing resins can be used alone orin the form of a mixture with another of these resins. Of these resinsepoxy monomers, epoxy resin of low polymerization, unsaturated alkydresin dissolved into vinyl type monomer, etc., produce excellentresults, and in the case of epoxy monomer or epoxy resin of lowerpolymerization, it is possible to carry out the process by using aplasticizer or like diluent. I

The photosensitive plate of this invention is, as aforementioned,characterized in that the photoconductive layer thereof comprises aphotoconductive substance and resin may comprise any, ma-

The polymerizable liquid resin precursors may comdispersed systemsandwiched between a conductive layer and a translucent insulativelayer, and composed of a solid layer prepared by polymerization of aliquid form resin of a mixture of photoconductive substance dispersed ina liquid form polymerizable resin not containing a solvent. Thephotosensitive plate of this invention can be produced in accordancewith the following process. A mixture prepared by dispersing fine powderphotoconductive substance into the mixture of one or more liquid formpolymerizable resins not containing a solvent, as mentioned above, isplaced between the conductive layer and the translucent insulativelayer, to form a sandwich, the thickness of such photoconductive layermixture is made uniform and thereafter, polymerization of the liquidform polymerizable resin is accelerated at an appropriate temperature toproduce a perfectly solid resin, and the photosensitive plate is therebyobtained.

According to this invention, in order to appropriately adjust the speedof polymerization of the polymerizable resin in producing photosensitiveplates, when the polymerization reaction is too slow, a polymerizationpromoter is added, and when it is too fast, a polymerization inhibitoris added. In case of, such as for example, methyl acrylic acid, wherepolymerization is promoted by the energy of radioactive rays, it ispossible to control radiation during the time when polymerization iscarried out. Also, when the viscosity of polymerizable resin is low, andthe viscosity of the mixture prepared by dispersing the fine powderphotoconductive substance thereinto, is low, and is not appropriate forproducing the photosensitive plate, prepolymerization is carried out bykeeping the mixture at an appropriate temperature to attain desirableviscosity, and thereafter it can be used in producing photosensitiveplates. In this case, the polymerizable resin, having been subjected toprepolymerization, is mixed with the fine powder photoconductivesubstance to prepare the paint form mixture and when the thus-obtainedpaint form mixture is applied as a coating, the same effect can beobtained.

Photosensitive plates having various properties can be obtained bychanging such conditions as quality, mixture ratio, thickness of theconductive layer, of the photoconductive layer composed of the mixtureof photoconductive substance and polymerizable resin, and of thetranslucent insulative layer, and photosensitive plates prepared inaccordance with the following conditions, present excellent propertieswith regard to contrast, sensitivity, sharpness and fogless image, andin addition to these properties, they exhibit satisfactory physicalstrength.

As the conductive substance, tin foil or aluminum foil whose thicknessis from to is preferable in view of conductivity, tensile strength andflexibility. Of course, in case of the photosensitive plate which doesnot require flexibility, it is possible to increase such thickness.

As the translucent insulative layer, polyester film whose thickness isfrom 10 to 30,, produces excellent results. When a film whose thicknessis below 10a is used, producing the photosensitive plate is difficult,and in carrying out the charging operation during use, breakdown readilyoccurs. Protection of the photoconductive layer is accordinglydeteriorated, and the durability of the photosensitive plate forrepeated use becomes poor. On the other hand, when a film whosethickness is above 30 is used, contrast or sharpness of the obtainedimage is poor.

As the photoconductive substance, zinc oxide, activated cadmium sulfideand cadmium selenate give excellent results, and as the liquid formpolymerizable resin not containing a solvent used as a binder for thefine powder photoconductive substance, epoxy monomer, epoxy resin oflower polymerization, and the solution of unsaturated alkyd resindissolved into vinyl type monomer, provide particularly excellentresults. Among these, especially when epoxy resin used as the binder,and activated cadmium sulfide or cadmium selenate is used as thephotoconductive substance, the ratio of the binder to thephotoconductive substance should be within the range from 10 to 20% byweight, and excellent results are obtained. When this ratio goes beyond20% the image formed on the photosensitive plate loses sharpness, foggyimages are produced, contrast becomes poor and photosensitivity isdeteriorated. When this ratio is below 10%, the viscosity of the mixtureof the fine powder of the photoconductive substance is remarkablyincreased, and producing the photosensitive plate is difficult.

When epoxy resin is used as the binder, excellent results are obtainedwhen an aliphatic amine, aromatic amine, or amine salt is used as thehardening agent, and the hardening speed is appropriate. In this case,the thickness of the photoconductive layer after completion ofpolymerization is appropriately from 30 to 200 4. When it is below 30the contrast of the image is deteriorated, and when the thicknessbecomes above 200,4, the contrast of the obtained image is high, butirregular or foggy images result.

When a solution of unsaturated alkyd resin dissolved in vinyl typemonomer is used as the binder, and activated cadmium sulfide or cadmiumselenate is used as the photoconductive substance, excellent results areobtained when the ratio of the binder to the photoconductive substanceand the thickness of the photoconductive layer after completion ofpolymerization are selected as mentioned above.

Examples of vinyl type monomers usable in this invention include styrol,vinyl acetate, methyl methacrylate, and diallylphthalate or the like.Examples of unsaturated alkyd resins include the polycondensationproduct of maleic acid anhydride, or fumaric acid and ethylene glycol orpropylene glycol etc.

When vinyl type monomer with unsaturated alkyd dissolved therein, isused, excellent results and appropriate hardening speed are obtained byusing an agent to promote hardening, such as benzoyl peroxide, or methylethyl ketone peroxide or such like catalyst, and naphthanic acid cobalt,or dimethyl aniline or such like hardening promoter.

In FIG. 2, rollers 4, 4' are made of metal or synthetic resins havingappropriate rigidity and are rotatably supported on parallel shafts 5,5' spaced by a predetermined interval. Rollers 4, 4' and shafts 5, 5control the thickness of the photosensitive plate, and the spacinginterval therebetween may be set to provide predetermined thickness ofthe photosensitive plate by adjusting the interval between the shafts 5,5. The photosensitive plate is comprised of thin film 6 of conductivesubstance, thin film 7 of translucent insulative substance, and mixture8 prepared by dispersing fine powder photoconductive sub stance in aliquid form polymerizable resin.

Thin film 6 is placed on one of rollers 4, 4', e.g. roller 4, thin film7 is placed on roller 4', and mixture 8 is placed on the concave portionbetween the two films to be pinched between thin film 6 and thin film 7and the whole is drawn in the direction shown by the arrow. Thereby,while the thickness of the photoconductive layer is kept uniform, thepolymerization of the polymerizable resin is completed, and thus athree-layer photosensitive plate in the form of sandwich with thephotosensitive layer pinched between the films is continuously prepared.

For controlling the thickness of the photosensitive plate, in place ofthe two rollers, other members such as two cutters with round edge canbe used, and instead of drawing the photosensitive plate from betweentwo rollers, the photosensitive plate may be fixed, and the two rollersmay be moved to produce the photosensitive plate.

In FIG. 3 base plate 9 having appropriate rigidity, such as metal orsynthetic resin, is provided, and the photosensitive plate comprisesthin layer 16 of conductive substance, mixture 18 prepared by dispersinga photoconductive substance in a liquid form polymerizable resin, andthin layer 17 of translucent insulative substance. Member 10 is providedfor controlling the thickness of the photosensitive plate and is in theform of rails made of a rigid substance, each rail being placed on anopposite end of thin layer 16. Cutter form member 11 has a round edgefor regulating the thickness of the photosensitive plate as member 11moves on rail form member 10, and thus a composite member forcontrolling photosensitive plate thickness is composed of members and11.

Thin layer 16 is placed on base plate 9, and on this layer 16 is placedthin layer 1-7. The end portion of layer 17 is fixed on thin layer 16 bytape 12 or the like. Next, mixture 18 obtained by dispersing the finepowder photoconductive substance in a liquid form polymerizable resinnot containing a solvent is disposed between said thin layers 16 and 17.Moving cutter member 11 round edge along the upper surface of thin layer17 on rail form member 10 squeezes the layers in the direction shown bythe arrow in FIG. 3a to form mixture 18 in desired thickness betweenthin layers 16 and 17, and while in this state, polymerization of saidpolymerizable resin is completed to produce the photosensitive plate.

In place of cutter member 11, roller 4 shown in FIG. 2, can be used, andthe same effect is also obtained by fixing cutter member 11 or roller 4and moving base plate 9 on which the photosensitive plate is placed. Theinterval between the members 4, 4' or 10, 11 for controlling thethickness of the photosensitive plate may be adjusted by appropriatemeans (not shown), for advantageously producing photosensitive plates ofvarious thicknesses.

The respective members used in producing the photosensitive plate arenot restricted to those shown in the drawing, but may comprise similarmembers which give the same effects and functions. The following are theexamples of photosensitive plates of the inventiombut the invention isnot restricted to these examples.

EXAMPLE 1 10 g. of cadmium sulfide activated by copper and halogen andhaving granularity of almost 1011-, 1.2 g. of epoxy resin Epikote 815(trade name of Shell Chemical Co., Ltd.) mainly composed of monomer, butcontaining dilnout and lower polymerized resin partially containing ofE. I. Du Pont De Nemours Co., Inc.) film whose thickness is 25,11. wasused, and between said two thin layers, said mixture for thephotoconductive layer was pinched in accordance with the method forpreparing the photosensitive plate shown in FIG. 3, and thephotosensitive plate was then prepared. In this case, a rail form memberwhose height was 1001.4 was used in order to make the thickness of thephotoconductive layer 75p.

The thus-prepared photosensitive plate was maintained at a temperatureof 70 C. for two hours, to promote the hardening reaction of epoxyresin, and then cooled to room temperature, and the photosensitive platewas thus completed.

Positive corona discharge of 6 kv. was applied to this photosensitiveplate, and then irradiation of a light image was carried out in a darkplace, while at the same time, 5.5 kv. of negative corona discharge wasapplied thereto. Then the whole surface of the photosensitive plate wasexposed, and the latent image was developed with toner having negativecharge. Copying paper was then pressed against the plate to transfer thepowder image thereon, and the transferred powder image was then fixed onthe copying paper to provide a printed image.

Such printed image was sharp, the contrast thereof The photosensitiveplate prepared: in accordance with the above-mentioned method hasremarkably strong resistance against bending and remarkable hardness ofthe film of the photoconductive layer when compared with thephotosensitive plates of the same kind produced by prior 7 arttechniques which use solvent, and therefore the photosensitive plateobtained in this method is not subject, in image transferring processesor cleaning processes, to

physical damage, which is a problem for conventional,

photosensitive plates.

From a number of experiments carried out in the past, it was known thatin the conventional methods in which solvent is used, small amounts ofvolatile components,

such as solvent or water content, are retained in the photosensitivelayer even after drying, and therefore when conventional photosensitiveplates are exposed to ambient deterioration of the latent image was notdetected, and

upon such ambient exposure, no change in the quality of such latentimage was observed. I

EXAMPLE '2 As in Example 1, a photosensitive plate was prepared inaccordance with the process shown in FIG. 2, and in order to providephotoconductive layer thickness of 75 the spacing interval between thetwo rollers was set at 115 and the photosensitive plate made in sandwichform was drawn therefrom. Such photosensitive plate was completed underthe same conditions as in Example 1, and

upon use provided excellent printed images.

EXAMPLE 3 In Example 1, cadmium selenate was used in place of cadmiumsulfide and excellent results were obtained in the same manner.

EXAMPLE 4 g. of cadmium sulfide, 15 g. of Rigolac No. 2004 (trade nameof Riken Synthetic Resin K.K.), which is a styrene monomer solution ofunsaturated alkyd resin, 2 g.

"of 14% styrene monomer solution of dimethyl aniline as the hardeningpromoter and 2 g. of benzoyl peroxidepaste as the catalyst, weresufficiently mixed to provide the photoconductive layer mixture. Byusing this mixture, a photosensitive plate was prepared in accordancewith the method shown in FIG. 3 in the same manner as in Example 1, andhardening of unsaturated alkyd resin was completed by maintaining thephotosensitive plate at 15 C. for about 40 minutes, and thephotosensitive plate was thus completed.

On using this photosensitive plate, a printed image was obtained throughthe same process as in Example 1, and the obtained image was remarkablysharp, of high contrast, and no fogginess was evident.

EXAMPLE 5 In Example 4, cadmium selenate was used in place of cadmiumsulfide, and a photosensitive plate was completed .in the same manner asin Example 4, and the excellent printed images were obtained.

, EXAMPLE 6 In Example 4, the preparation of the photosensitive platewas carried out in accordance with the method of FIG. 2 with the spacinginterval of the two rollers set at p to provide a photoconductive layerthicknes of 75 This photosensitive plate produced excellent images.

9 EXAMPLE 7 100 g. of cadmium sulfide, 20 g. of methacrylic acid methylester monomer, and 0.4 g. of benzoyl peroxide were sufficiently mixed toprepare the mixture for the photoconductive layer and using thismixture, a photosensitive plate, made in accordance with the methodshown in FIG. 3 as in Example 1, was maintained at 60 C. for about onehour, and the polymerization of methacrylic acid methyl ester wascompleted to provide the photosensitive plate. This photosensitive platewas used to produce the printed images by the same process as in Example1, and the produced printed images were excellent.

EXAMPLE 8 Epoxy resin Shell Epikote 834, which is mainly composed of themixture of monomer and dimer, was used, and a photosensitive plate wasprepared in the same manner as in Example 1, and printed images producedby the same process, were excellent.

EXAMPLE 9 100 g. of cadmium sulfide, 18 g. of the mixture obtained bydissolving 10 parts of vinyl acetate resin into 100 parts of Epikote828, and 3.6 g. of the hardening agent H-92 (trade name of JapanSynthetic Industry K.K.) were sufiiciently mixed, to prepare a mixturefor the photoconductive layer and by using this, a photosensitive platewas prepared in accordance with the method shown in FIG. 3 in the samemanner as in Example 1. This photosensitive plate was maintained at 25C. for 40 hours, and polymerization was completed. In using thisphotosensitive plate, +8 kv. corona discharge was applied to thetranslucent insulative layer, and then 6 kv. A.C. corona discharge wasapplied thereto and at the same time irradiation of a light image wascarried out. Uniform light was thereafter irradiated on the wholesurface of the photosensitive plate, and then the static latent imagewas developed with developer. In order to make image transfer excellent,+6 kv. corona discharge was carried out, and then copying paper waspressed against the image surface to carry out image transfer. Theprinted image transferred on the copying paper was fixed by thermaltreatment. The obtained image was remarkably sharp, of high contrast andno fogginess was evident. Developer remaining on the photosensitiveplate was cleaned with a cloth, and the photosensitive plate was usedrepeatedly, and the image on the photosensitive plate was notdeteriorated.

As has been explained so far, according to this invention, it ispossible to produce photosensitive plates in an economical, safe andsanitary manner, and such plates produce images of high contrast inaccordance with the methods for forming images of the precedingexamples. The sensitivity thereof is high, no fogginess is evident, andit is possible to produce sharp images. The physical strength of suchphotosensitive plates is excellent, and resistance against bending isremarkably higher than that of conventional three-layer photosensitiveplates.

The durability of the photosensitive plate against change with passageof time and in repeated use is excellent, and in this respect thepractical value of the photosensitive plate of this invention is high.Since no solvent is used, there is no likelihood of solvent injury tothe human body or of fire and the photosensitive plate of this inventionhas remarkable efiects.

This invention is not restricted by the descriptions of thespecification or the examples, but embraces those improvements ormodifications within the spirit of this invention.

What is claimed is:

1. An electrophotographic plate comprising a photoconductive layercomposed of a photoconductive material dispersed in a resin binderdisposed between and integrally bonded to a conductive layer and atranslucent insulative layer, said photoconductive layer being a solid10 layer formed by disposing a layer of a solvent-free liquidpolymerizable binder resin precursor containing said photoconductivematerial dispersed therein between a conductive and an insulative layerand converting the liquid polymerizable resin precursor into a solidresin while in contact with the conductive and insulative layers.

2. The electrophotographic plate according to claim 1 wherein thepolymerizable binder resin precursor is a polymerizable synthetic resinmonomer.

3. The electrophotographic photosensitive plate according to claim 2wherein the polymerizable synthetic resin monomer is epoxy monomer.

4. The electrophotographic plate according to claim 1 wherein thepolymerizable resin is polymerizable synthetic resin of lowerpolymerization.

5. The electrophotographic plate according to claim 4 wherein thepolymerizable synthetic binder resin of low polymerization is lowpolymerized epoxy resin.

6. Electrophotographic plate according to claim 4 I wherein thepolymerizable synthetic binder resin of lower polymerization is lowpolymerized epoxy resin, the photoconductive substance is at least onesubstance selected from the group consisting of cadmium sulfide andcadmium selenide, and the ratio of epoxy resin to the photoconductivesubstance is 10 to 20% by weight, and the thickness of thephotoconductive layer after the polymerization is from 30 to ZOO/1..

7. The electrophotographic plate according to claim 1 wherein the liquidpolymerizable binder resin comprises a mixture of polymerizablesynthetic resin monomer and other resin dissolved therein.

8. The electrophotographic plate according to claim 7 wherein thepolymerizable synthetic resin monomer is vinyl type monomer and theother resin is unsaturated alkyd resin.

9. The electrophotographic plate according to claim 8 wherein thephotoconductive substance is at least one substance selected from thegroup consisting of activated cadmium sulfide and cadmium selenate, andthe ratio of the .vinyl type monomer with said unsaturated alkyd resindissolved therein to said photoconductive substance, is 10 to 20% byweight, and the thickness of the photoconductive layer after thepolymerization is from 30 to 200p.

10. The electrophotographic plate according to claim 1 wherein theliquid polymerizable binder resin comprises a mixture of polymerizablesynthetic resin of low polymerization and other resin dissolved therein.

11. The electrophotographic plate according to claim 1 wherein thephotoconductive material is selected from the group consisting ofactivated cadmium sulfide and cadmium selenate.

References Cited UNITED STATES PATENTS 3,251,686 5/1966 Gundlach 117-218X 3,447,957 6/1969 Behringer 961. 8 X 3,077,398 2/1963 Jones 961.8 X3,438,706 4/1969 Tanaka et al 961 UX 3,457,070 7/ 1969 Watanabe et al961 X 3,501,330 3/1970 Cassiers et al 961.5 X 3,536,483 10/1970 Watanabeet al. 961.5 X 3,175,091 3/1965 Cherofi et a1. 961.5 3,393,070 7/1968Snelling 96-1-5 3,397,086 8/1968 Bartfai 961.5 X 3,408,184 10/1968Mammino 96-15 3,442,781 5/1969 Weinberger 961.5 X

OTHER REFERENCES Dessauer et al., Xerography and Related Processes,1965, p. 96-97.

GEORGE F. LESMES, Primary Examiner J. R. MILLER, Assistant Examiner U.S.Cl. X.R.

